Triple shocks do like a long jump. I think they actually state no less than .050 to be safe pressure wise.
My favorite deer rifle is my Mark 5 Accumark in 257Wby. The free bore in a Weatherby isn't a concern. My 257 shoots a couple loads into the .2's. It likes the 75 grain VMax's at 3950 fps and the Nosler 110 Accubonds at 3450 fps.
It's not like the bullet is jumping unsupported. It is well supported and just gets a running start at the rifling. If revolvers can do it with their sloppy tolerances no reason a precision job in a rifle won't work.
Just looking but never actually measured the 300 RUM seems to be just as much freebore . Don't get sucked into someone trying to "make it better" by doing one with no free bore. A local guy had a Winchester Model 70 rebarreled in 257Wby with no free bore and it lasted about 3 shots with factory ammo before it blew up destroying everything including embedding a bit of metal in his face.
Weatherby makes for a pretty good shooter right out of the box and they respond favorably to simple accuracy mods.